The problem surfaced when I installed a yellow HP ink cartridge (Walmart purchase) into the printer head carriage. The printer has worked well since I acquired it four years ago. HP 7740 desk jet pro error message: "print head missing or installed incorrectly". I never disturbed the printer head and certainly didn't remove it. I have been without a printer for two weeks now. I've removed the cartridges and cleaned them several times. in the process I have moved them out and then in again. I have performed the reset several times and nothing has changed the status of the machine. I ordered a replacement printhead from HP and it can't be the correct one; got to deal with that now. It has been impossible trying to get to a real person at HP.
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